The present invention relates to a numerically controlled writing instrument with a carriage mounting a stylus holder with the carriage being movable over a writing plane with two drives for the stylus holder arranged approximately perpendicularly to one another. The drives convert path information into writing movements.
In numerically controlled writing instruments, it is desirable, from the viewpoint of the user, to be able to program immediately, if required, in addition to the usual character and symbol collections which can be called up via the keyboard of the device and are fixed permanently in sets by storage on exchangeable data carriers, further characters and symbols which are only of interest to the user or only of temporary interest, but can be made available within a short time.
It is known from the brochures Rotring NC-Schreiber and Held deltascript CNC, disclosed in U.S. Pat. No. 4,455,751 to file permanently symbols for a specific field on electrical or similarly programmable data carriers, for instance, electrically or electromagnetically programmable memories, and provide the memories in the form of a cassette and to equip the writing instrument control with plug-in devices so that the user can rapidly replace a cassette whereby the required symbol collection is available. The disadvantage of this device is the necessity that the symbol collection required by the user must be programmed by the manufacturer of the writing instrument and though the symbols may be only required for a short time they must be available on the cassettes supplied with the writing instrument. The time required for obtaining a collection of such symbols may be much longer than the time period in which the symbols are needed.
In so-called flat bed plotters, such as disclosed in the brochure of SG stanoplott III, which are also used for designations and plan designs with symbols for a particular field, it is known to file with the plot control programmed symbols for the particular field on a tape cassette and to transfer them, if required, into the direct access memory of the control. The disadvantage of such a solution is the expenditure for the mechanism and control used for recording and retrieval of the digital information defining the symbols from the tape as the data carrier.